1. Field of the Invention
This invention relates to the information introducing device of an electronic flash unit.
2. Description of the Prior Art
An electronic flash unit to be mounted on a camera to illuminate an object has recently become designed to exchange a plurality of bits of information with the camera and moreover, the types of information are in a tendency toward increase. The information transmitted includes a synchro signal produced in response to the shutter mechanism of the camera, a charging completion signal of the flash unit, and a signal warning of the impropriety of the set value of the shutter speed of the camera and in addition, in an electronic flash unit having the function of automatically controlling the quantity of emitted light so as to be fit for the object being photographed, information such as film speed and aperture value supplied from the camera body. Such information is usually transmitted as electrical signals through a plurality of electrical contacts provided in the coupling portion between the camera and the flash unit. However, as the types of information exchanged increase, the number of the electrical contacts and the number of the electric circuits including the electric circuit necessary for the supply of the information and the electric circuit necessary for the detection of the information increase to complicate the device.
On the other hand, some of such information is manually set by moving or displacing an operating member provided on the camera body or the flash unit. In most cases, the setting of exposure factors such as, for example, film speed and shutter speed is accomplished by rotating a dial device provided on the upper portion of the camera body. In U.S. Pat. No. 4,251,147 (German Pat. No. 29,16,353), applicant has proposed the technique of transmitting the amount of displacement of the film speed setting dial on the camera body to the flash unit inresponse to the mounting of the flash unit onto the camera.